Field of the Invention
The embodiments of the present disclosure relate to a light bar adhesive tape, more particular, to a light bar adhesive tape of the backlight source.
Description of the Related Art
Recently, a backlight unit of a smart phone has a development trend of “narrower”, “thinner” and “brighter”. A light emitting diode (LED) used in the backlight bar adhesive tape of the smart phone emits light laterally, and the incidence distance is in a range between 1.5 mm and 3.0 mm. A light-emitting surface of the LED has a height of about 0.5 mm and a width of about 3.0 mm, that's to say, a single LED light source is approximately acted as a point light source (the LED has a normal incidence in a light guide plate, and the light intensity and the brightness thereof are constant), according to the illuminance equation of a point light source
      E    =                  I        *        cos        ⁢                                  ⁢        i                    R        2              ;      I    =          φ      ω        ;in which φ is the luminous flux, ω is the spatial angle, I is the light intensity, R is the distance from the light source to the light guide plate. It can be determined from the above equation that, the illuminance created in a certain area illuminated by a point light is in direct proportion to the light intensity of the light source, but is in inverse proportion to the square of the distance from the light source to the illuminated area. Therefore, it causes inevitably the phenomena of bright band and hot spot on the incident light side of the backlight source.
The bright band on the incident light side of the backlight source cannot be notably improved merely by a mesh in the light guide plate and V-CUT. If a backlight source with a black light bar adhesive tape of rectangular ring shape is merely used, an average brightness of the backlight source will be reduced by about 10%, thereby the optical specification of the backlight source cannot reach the standard value required by the recent market. Further, a press on the incident light side of the backlight source will further reduce the average brightness of the backlight source by 3% to 5%.